Secondary frequency control in power systems with arbitrary communication delays

Abstract

In this paper, we consider a Kron-reduced microgrid that consists solely of generator units. The frequency control we consider consists of primary droop control at the generator units, as well as distributed averaging integral (DAI) control that enforces both synchronization among the generator frequencies and optimal power dispatch. To any generating unit, a DAI controller is attached that exchanges information with neighboring nodes. In practice, this is subject to time delays, which impedes the stability analysis. By performing scattering transformation of the input and output variables at each end of the communication link between two DAI controllers, and trans -mitting the scattered variables instead of the controller output, stability of the nominal frequency is guaranteed. The time delays are not restricted to any bounds